"We will keep what works and fix what doesn't in city government so our people emerge stronger," she said after a brief ceremony at City Hall.

Rawlings-Blake, who had been president of the City Council for the past four years, assumes the office vacated by Sheila Dixon, who resigned as part of a plea deal resolving her criminal case.

"None of us asked for this moment, but all of us must accept the challenges and hard work that come with it," Rawlings-Blake said.

The daughter of the late Del. Howard P. Rawlings, a renowned state leader, she became the youngest person ever elected to the council in 1995 at age 25.

Rawlings-Blake has vowed to strengthen ethics laws and maintain public safety while addressing a record budget shortfall. About 150 city residents have been assigned to transition teams to conduct a "robust and comprehensive review" of city government, she said. A report of their findings is to be released March 5.

Two of Dixon's deputy mayors, Andrew B. Frank and Christopher Thomaskutty, will remain in their current jobs. Whether Deputy Mayor Salima S. Marriott will stay is unclear.

Dixon's spokesman, Scott Peterson, and chief of staff, Demaune Millard, were not retained, along with other members of the Dixon administration, including many from the office of neighborhoods.

The venerable City Hall building appeared very much in transition Thursday as movers bustled about with dollies and stacks of boxes. While Dixon had agreed a month ago to resign, she had remained in office until Thursday, when she was officially sentenced to probation and community service after being convicted of embezzlement and pleading guilty to perjury.

At City Hall, workers hoisted a new blue seal bearing the words "Mayor Stephanie Rawlings-Blake" in the mayor's conference room. In the entranceway, Dixon's photograph had been removed and Rawlings-Blake's hung in its place.

The city Web site was down for at least an hour and relaunched bearing the name and face of the new mayor.

Rawlings-Blake, 39, wasted little time in getting down to business, convening a meeting of agency heads and other Cabinet members Thursday afternoon.

"One of the first things I want to make clear is how I like to operate," she said. "And that is with mutual respect. There is no room, particularly in this time for our government for 'them against us.' I am a firm believer in collaboration and ... I hope that your work for the city reflects that as well."

There are vacancies in the top positions at three city agencies, which many attribute to the cloud that has hung over City Hall during the past year. It is unclear how many agency heads will remain permanently and how many will be employed on a contingency basis. The new administration has not issued a list of current staff members.

She asked Cabinet members to aid the new council president so that he might have the "same seamless transition that was afforded to me."

Bernard C. "Jack" Young, a 14-year veteran of the City Council, is expected to be elected its president at Monday's meeting. At least nine of the 14 council members have announced their support for him.

Until then, Edward L. Reisinger, the council's vice president, will serve as acting president. Thursday afternoon, he sat in the president's seat in council chambers, joined by several council members, as he practiced the protocol for officiating at Monday's meeting.

Earlier, the city's clerk of court, Frank M. Conaway, administered the oath of office to Rawlings-Blake, who was surrounded by her immediate family, including her mother, Dr. Nina Rawlings, and husband, Kent Blake.

When Conaway instructed Rawlings-Blake to raise her right hand and place her left on the Bible, her 6-year-old daughter, Sophia, did the same.

It was a moment of levity in an otherwise austere ceremony. Only relatives, selected city officials, including the City Council members and Comptroller Joan M. Pratt, and members of the news media were invited into the opulent mayor's ceremonial room for the event.

The mayor's daughter, mother and husband wore matching shades of dove and charcoal gray. The girl whispered "Mommy!" and handed her mother a corsage of yellow lilies as the ceremony was about to begin.

An elderly aunt, Rebecca Scott, the sister of the mayor's father, collapsed after a prayer offered by the Rev. Bruce Haskins, a cousin of Rawlings-Blake's. The incoming mayor caught her aunt and helped her into a chair.

Scott revived and mouthed "I'm sorry" to her niece. After the ceremony, paramedics arrived to attend to her.

Rawlings-Blake signed her name in a registry of mayors in a large, leather-bound book. Immediately above her name was a the signature of Sheila Dixon - large and full of flourishes - and accompanied by the notation "a term of four years to expire Dec. 6, 2011."